Does Blender have a transform modifier (such as scaling, rotation, translating)?
Alt-S will undo scaling (ie. set scale factors to 1.00)
Alt-R, and Alt-G will, in the same way, undo rotation and translation respectively.
In that sense, S,R, and G are not permanently changing your mesh objects.
If you want to make transformations permanent, Ctrl-A and Apply rotation etc.
Does that answer your question?